The IEEE 802.21 standard defines mechanisms and procedures that aid in the execution and management of inter-system handovers. IEEE 802.21 defines three main services available to Mobility Management applications, such as Client Mobile Internet Protocol (Client MIP) or Proxy MIP. Referring to FIG. 1, these services are the Event Service 100, the Information Service 105 and the Command Service 110. These services aid in the management of handover operations, system discovery and system selection by providing information and triggers from lower layers 115 to upper layers 120 via a media independent handover (MIH) function 125.
Within the context of the command service 110, functionality is defined for querying an MIH compatible node to determine the node's Internet Protocol (IP) capabilities. This is accomplished via the MIH_Network_Address_Information Request message sent from a wireless transmit/receive unit (WTRU) and the MIH_Network_Address_Information Response message sent from the MIH compatible node.
Certain systems, such as the Third Generation Partnership Project Long Term Evolution (3GPP LTE) system, utilize a hybrid mobility schema where both client MIP and proxy MIP are used. Proxy MIP is preferred because of its well known advantages such as elimination of over-the-air (OTA) tunnelling overhead, greater flexibility, and reduced latency. However, in a roaming scenario it is highly likely that a WTRU will encounter networks that do not support proxy MIP. In this scenario, client MIP is used.
Under the current IEEE 802.21 standard, a WTRU is unable to determine whether an accessible network provides support for localized mobility procedures (such as proxy MIP) or only conventional mobility procedures (such as client MIP). This information is an important criterion in network selection. Selection of a network with undesirable mobility management procedures will result in sub-optimal mobility scenarios. Furthermore, if a WTRU is able to determine the MIP characteristics of a network, the WTRU may trigger IEEE 802.21 procedures to improve mobility handling.